All yachts of any reasonable size need to be registered. The chosen flag state is most important and needs careful consideration due to the many variables involved.
The owner needs to protect his interest, but most likely does not want to burden himself or his crew with unwelcome bureaucracy. Similarly, he may desire to insulate himself fiscally and legally from the vessel, for commercial or asset preservation purposes.
The requirements for commercially operated vessels ( in this case, charter yachts ), are more demanding, and require special consideration to avoid expensive errors.
Blue Ensign are experienced with yacht registration, and deal with the practical requirements working with your lawyers or marine managers, or completing all of the registration process on your behalf.